Prevent use-after-free bugs in object variants. Fixes bug #20305 #20300
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the bug happens specifically when deleting an item in a seq. The item taking it's place might not have the same case fields. Then =sink(x[i], move x[xl]) might leave the deleted fields still in memory! If the new item switches branches again, you get a use-after-free bug.
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The alternative solution is to turn discriminant destructor into a sink that resets the memory of cased fields AFTER instead of before assigning the discriminant. |
planetis-m
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planetis-m
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Thanks for your hard work on this PR! Hint: mm: orc; threads: on; opt: speed; options: -d:release |
narimiran
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Sep 6, 2022
) [backport] prevent use-after-free bugs in cased objects the bug happens specifically when deleting an item in a seq. The item taking it's place might not have the same case fields. Then =sink(x[i], move x[xl]) might leave the deleted fields still in memory! If the new item switches branches again, you get a use-after-free bug. (cherry picked from commit 8dcf367)
capocasa
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Mar 31, 2023
(nim-lang#20300) [backport] prevent use-after-free bugs in cased objects the bug happens specifically when deleting an item in a seq. The item taking it's place might not have the same case fields. Then =sink(x[i], move x[xl]) might leave the deleted fields still in memory! If the new item switches branches again, you get a use-after-free bug.
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